Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) result from a common pathogenic process: pulmonary injury or infection triggers an overwhelming inflammatory response (cytokine storm) that results in increased endothelial and epithelial permeability and efflux of inflammatory cells, protein, and water from the vascular system into the alveolar space. The incidence of ALI is estimated to be approximately 79 cases per 100,000 person-years. The treatment for those afflicted remains largely supportive with a mortality rate of approximately 40%. We have demonstrated that the small GTPase, Arf6, is a convergence point in the signaling pathways of several inflammatory mediators and cytokines with demonstrated involvement in ALI/ARDS. Activation of Arf6 into its GTP-bound state induces vascular leak and edema, which play major roles in the pathophysiology of ALI/ARDS. Thus, we hypothesize that pharmacological inhibition of Arf6 provides an opportunity to combat actions of multiple cytokines in ALI/ARDS, an approach which may be more effective than targeting single pathways with highly specific inhibitors. This rationale is supported by the encouraging preliminary in vivo data generated with our small molecule inhibitor of Arf6, NAV-2729, in a murine model of lipopolysaccharide (LPS)- induced ALI. This phase 1 SBIR will improve upon our current NAV-2729 series of Arf6 inhibitors through an in silico molecular modeling effort to identify compounds with improved potency and hydrophilicity. We will determine potency in a biochemical nucleotide exchange assay and verify activity in a mechanism-based cellular Arf6 pulldown assay. Compounds with an optimal mix of potency and hydrophilicity will be screened in vivo to determine pharmacokinetic (PK) parameters. We will then demonstrate proof-of-concept efficacy in the murine LPS-induced ALI model. Successful completion of these activities will accomplish two very important goals. First, it will provide proof- of-concept that inhibiting Arf6 is a promising novel approach for treating ALI/ARDS. Second, it will position us to continue medicinal chemistry optimization of Arf6 inhibitors in Lead Optimization activities in phase 2 (optimization of potency, selectivity, solubility, ADMET properties, patentability). Successful completion of this development program may result in a therapy effective for treating humans with ALI/ARDS.